Conventionally, image forming apparatuses employing an electrophotographic system such as a copier, a printer, and a facsimile machine has been widely known. In such image forming apparatuses, an electrostatic latent image is formed on a surface of a photoreceptor. The electrostatic latent image is developed with toner, and a toner image thus obtained is transferred and fixed onto a sheet such as a paper sheet or the like. The toner used to develop the electrostatic latent image is supplied from the developing device to the surface of the photoreceptor. To the developing device, toner is supplied from a toner cartridge via a toner transport device. In a structure in which a toner cartridge is disposed over a developing device, a toner transport device is provided with a toner transport path extending in an up-and-down direction.
On the other hand, in recent years, with the improvement in high image quality of image forming apparatuses, particles of toner have been designed to have a micro diameter. Toner having such micro particles generally does not have good fluidity, so that retention and solidification of toner easily occur in a toner transport path of a toner transport device. In order to overcome such a problem, a toner transport device needs some contrivances.
For example, an apparatus disclosed in patent document 1 is arranged such that an accordion pipe is used as a toner transport member constituting a toner transport path disposed in the up-and-down direction, and an outer surface of the accordion pipe is repeatedly hit so as to cause toner remaining in pleats of the inner surface of the accordion pipe to fall off. However, the toner transport member constituted of the accordion pipe, structurally, does not easily prevent retention and solidification of toner in a toner transport path.
Further, patent document 2 discloses an apparatus in which, inside a toner transport path disposed in an up-and-down direction, a spring agitator is provided that moves in upward and downward directions so as to prevent the toner from adhering to the inner wall of the toner transport path. However, this structure raises such a problem that toner easily remains and solidifies on the surface of the spring agitator.
In patent document 3, the inventors previously proposed a toner transport device which vibrates, in upward and downward directions, a toner transport member constituting a toner transport path disposed in an up-and-down direction. According to this arrangement, the whole toner transport member is evenly vibrated upward and downward, so that it is possible to properly prevent retention and solidification of toner in the toner transport path.
Incidentally, in such an arrangement that the toner transport member is vibrated in upward and downward directions, an elastic member for absorbing oscillation caused by vibration at the time of expanding and contracting operations of the toner transport member is provided on a joint section between the toner transport member and a socket thereof. Further, the elastic member requires a function for preventing toner from leaking from the joint section without hampering the upward-and-downward vibration of the toner transport member. The toner leakage causes internal taint or foggy image.
Conventionally, as such an elastic member having a toner sealing property, a member obtained by applying a synthetic leather to the elastic member is disclosed by patent document 4 for example. The elastic member is to prevent toner from leaking from an end of a cleaning blade. As the elastic member, it is preferable to use Moltplane (trade name) obtained by processing urethane rubber into a porous sponge manner. As the synthetic leather, it is preferable to use Ecsaine (trade name: product of Toray Industries) obtained by blending micro polyester fibers with polyurethane and processing the mixture into a back skin manner. In applying the elastic member with the synthetic leather, a double-face adhesive tape is used.
Further, patent document 5 discloses, as the elastic member having a toner sealing property, foamed polyurethane whose density is 20 to 40 (kg/m3) and cell number is 40 to 60 (in every 25 mm). The elastic member comes into contact with a toner layer thickness restricting member of a developing device from a side opposite to a toner carrier so as to prevent toner from leaking from an end of the developing device.
Patent document 1: Japanese Unexamined Patent Publication, No. 174467/1992 (Tokukaihei 4-174467, publication date: Jun. 22, 1992)
Patent document 2: Japanese Unexamined Patent Publication, No. 296731/2001 (Tokukai 2001-296731, publication date: Oct. 26, 2001)
Patent document 3: Japanese Unexamined Patent Publication, No. 267945/2006 (Tokukai 2006-267945, publication date: Oct. 5, 2006)
Patent document 4: Japanese Unexamined Patent Publication, No. 174885/1992 (Tokukaihei 4-174885, publication date: Jun. 23, 1992)
Patent document 5: Japanese Unexamined Patent Publication, No. 137382/2000 (Tokukai 2000-137382, publication date: May 16, 2000)